1. Field
The present invention relates to a substrate assembly for crystal growth and a fabricating method of a light emitting device using the same. More particularly, the present invention relates to a substrate assembly for crystal growth including a bonding layer and a is fabricating method of a light emitting device using the substrate assembly.
2. Discussion of the Background
In general, since Group-III-element nitrides, such as GaN and AlN, have an excellent thermal stability and a direct-transition-type energy band structure, the Group-III-element nitrides have recently come into the spotlight as materials for light emitting devices in visual and ultraviolet regions. Particularly, blue and green light emitting devices using InGaN have been used in various applications such as large-sized full-color flat panel displays, traffic lights, indoor illumination, high-density light sources, high-resolution output systems and optical communications.
Since it is difficult to fabricate a homogeneous substrate that enables such a Group III-element nitride semiconductor layer to be grown thereon, the Group III-element nitride semiconductor layer has been grown on a heterogeneous substrate having a similar crystal structure using a process such as metal oxide chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). For example, a sapphire substrate is used as the heterogeneous substrate. That is, if MOCVD is used to fabricate a nitride semiconductor layer, an epitaxial layer of GaN semiconductor crystals is grown on a sapphire substrate by supplying an organic metal compound gas as a reaction gas into a reaction chamber in which the sapphire substrate is mounted as a growth substrate and maintaining the crystal growth temperature to be a high temperature of about 900 to 1100° C.
Meanwhile, the size of the substrates commercialized as growth substrates is is about 2 inches, but it tends to be gradually increased because of the mass production and the reduction in the fabrication cost.
However, the bending of a substrate depending on the crystal growth temperature is necessarily considered during the crystal growth. Accordingly, the thickness of the substrate is gradually increased as the size of the substrate is increased.
Accordingly, in order to use a dicing process of cutting a growth substrate into individual chips after the crystal growth is completed, the thickness of the substrate is necessarily decreased from 450 μm to 100 μm, for example, for a 2-inch substrate, through a lapping process. As the size and thickness of the substrate is increased, the time and the cost spent for the process are increased.
Further, if the substrate is thick during the crystal growth, the temperature variation in the substrate is increased. For example, the large temperature difference between top and bottom portions of the substrate may allow cracks to be generated in the substrate.
Therefore, even though the size and thickness of a substrate for growing a light emitting device is increased, it is required to develop a substrate assembly for crystal growth, which can prevent the time and the cost required for a fabricating process of the light emitting device from being excessively increased and prevent the cracks in the substrate during the crystal growth from be generated.